SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'e6c4a92bfa9e31988d394d58261915d9fc67cb4698cecc3eea04483927edaf58' 
  AND token = '8phhjVyMnaHJUKeSaDe4lmin7EZV6dn51XYSxIDvYW0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

{
  "query_block": {
    "select_id": 1,
    "message": "no matching row in const table"
  }
}